Frequency changer system



Julyll, 1933. E. T. BURTON FREQUENCY CHANGER SYSTEM Filed Oct. 4, 1928 i5 v C I BIAS OFC 5M; 0 5

Wl/ENTUR EVERETT Z' BURTON 5) ATTUENEY Patented July 11, 1933 UNITED.STATES PATENT OFFICE EVERETT '1. BURTON, OF HILLBURN, NEW JERSEY,ASSIGNOB T0 BELL TELEPHONE LABORATORIES; INCORPORATED, OF NEW YORK, N.1., A CORPORATION OF NEW YORK FREQUENCY CHANGER SYSTEM Application filedOctober 4, 1928. Serial No. 310,238.

This invention relates to frequency changer systems where staticfrequency-transformers are employed for increasing the frequency of analternating current.

An object of this invention is to increase the frequency of analternating current without introducing certain types of distortion inthe current wave of increased frequency. A feature of the inventionresulting from the accomplishment of this object resides in the factthat the new frequency has substantially no current components of evenorders of harmonics present therein.

Various types of frequency multipliers are known in the art, the mostgenerally known types being rotary generators and the static orstationary frequency-(ransformers. Ptotary generators, particularlythose which are designed to yield appreciable amounts of energy, entailconsiderable expense especially in systems employing high frequencies.The static frequency-transformers, to which the present inventionrelates, are particularly adaptable to use in signaling systemsemploying relatively high frequencies and in this field have been usedto a large extent because of the economy effected and the efliciencywith which the increase in frequency is obtained. Heretofore, in systemsemploying transformers for increasing the frequency, the chief concernwas the production of harmonics which. when superimposed on thefundamental frequency, would result in the desired frequency. Thecurrent wave thus produced might be constituted of both the odd and evenmultiples of the new frequency and in order to eliminate the distortionintroduced by the even multiples it was necessary to employ numerouscomplex networks which required frequent adjustments. Furthermore, inthese systems the increase in frequency effected in a single step wasrelatively small. such as the doubling "or tripling of the fundamental,and if it were desired to obtain a much higher frequency the operationinvolved in the single step had to be repeated several times.

S'tatic frequency-transfru'mers employed in accordance with the presentinvention are capable of producing relatively high frequencies in asingle step and when very high frequencies are desired they may bereadily had by repeating the first step a less number of times thanheretofore were needed with transformers.

A feature of the invention is the production of secondary impulses whichmay be so spaced that the new frequency may be an even or odd multipleof the fundamental as de sired. I

Another feature is the substantial elimination of all even multiples ofthe new frequency thereby avoiding the distortion due to such multiples.

Another feature resides in the fact that the lowest frequency voltageappearing in the secondary circuit is that of the desired multiplefrequency.

The invention will he better understood by reference to the followingdetailed description taken in connection with the accompanying drawingin which:

Fig. 1 shows in schematic form the arrangement of a pair of staticfrequency-transformers for increasing the fundamental frequency twofold;

Fig. 2 graphically represents the input current of the fundamentalfrequency, the secondary voltage, and the output current of the doublefrequency in the arrangement shown in Fig. 1;

Fig. 3 shows a modification of Fig. 1 wherein the fundamental frequencyis increased threefold;

Fig. at illustrates current and voltage waves of the arrangement shownin Fig. 3;

Fig. 5 shows a modification of Fig. 3 whereby the fundamental frequencyis increased fivefold;

Fig. 6 represents the wave forms and the changes effected in increasingthe frequency by the arrangement of Fig. 5; and,

Fig. 7 shows a combination of the arrangements shown in Figs. 1 and 5whereby the fundamental frequency is increased ten times and thenimpressed on the grid circuit of a vacuum tube amplifier.

In the following detailed l'lescription like material, such aspermalloy,

numbers represent like parts and theoretically ideal cases are discussedwith the understanding that departures from ideal conditions alwaysresult from the limitations of apparatus, non-linearity of magnetizationcurves, etc.

Referring to Fig. 1 an alternating current of a certain frequency isreceived over con-- ductors 11 and 12 from a source f of frequency andpassed through the primary windings 13 and 14 of a pair of high per-'meability transformers 15 and 16 which are of the type disclosed inapplicants copending application corresponding to British Patent312,338, accepted June 10, 1930. The cores of these transformers areoppositely biased by direct current of a value less than the maximumvalue of the alternating current, from source 17 through windings 13 and14. Thus, while in one transformer the alternating and direct currentcomponents may be aiding, in the other they will be opposed and willneutralize each other twice during a half cycle when the alternatingcurrent passes through values equal to that of the direct current.

The transformer cores are of a magnetic which has a very highpermeability at low magnetizin forces, and which consequently very soonecomes saturated when those forces are increased, with the result thatthe permeability is again reduced to a very low value. Since the mutualinductance between the primary and secondary windings of a transformeris directly proportional to the permeability of the core it is evidentthat by using a biasing arrangement such as shown in Fig. 1 the mutualinductance of each transformer may be controlled to have two maximaduring a half cycle of the alternating current, namely, at those valuesof this current at which the magnetizing force is zero.

Considering now the E. M. F. induced in the secondary windings, it is awell known fact that this E. M. F. is directly proportional to the rateof change of the primary current and to the mutual inductance.Therefore, when, as in the present arrangement, very reat variations ofthe permeability take p ace with correspondingly great variations inmutual inductance, the effect of the rate of change in current may beinsignificant except at such times when the mutual inductance akes onvalues appreciably higher than those prevailing during saturationconditions. Even at such times an. increase in mutual inductance maymore than offset a decrease in the rate of change of primary current.Thus at those instants when the alternating and direct currents in thetransformer windings nearly neutralize each other the mutual inductancewill be so high that an appreciable E. M. F. will be induced in one ofthe secondary windings. At any other times, whet-her when one currentpredominates over the other or when they aid each other, the corematerial will be saturated and the permeability and mutualinductancewill Therefore, when the alternating current rises from zero in theopposite direction to the biasin current in one of the transformers 15and 16. no secondary E. M. F. will be induced until its value approachesthat of the biasing current. The mutual inductance then increases manyfold and a voltage impulse is induced which lasts until the alternatingcurrent exceeds the biasing current by a small value. At this time themutual inductance is again reduced and no secondary E. M. F. occursuntil the decreasing alternating current again approaches the biasingcurrent in value when another voltage impulse will occur. However, sincethe current now is decreasing this impulse will be of the oppositepolarity of the first impulse. As the alternating current now continuesto drop to its zero value and then rises through values of the oppositepolarity, two impulses of voltage of opposite polarities are generatedin the other of the secondary windings. Due to the reversed connectionsof windings 18 and 19, as shown in the drawing, the impulses produced inwindin 19 are reversed so as to form with the impulses produced inwinding 18 a series of impulses of alternate polarity, two impulses ofopposite polarities being produced by each half cycle of alternatingcurrent in windings 13 and 14. By the insertion' of suitable networkssuch as constituted of condensers 20 and 21 and inductance coil 22 inthe output circuit 27 of the transformer, a series of secondary currentimpulses may be produced in circuit 27 which are smoothed out to form asinusoidal wave of a frequency double that of the alternating current inthe input circuit comprising conductors 1]. and 1 In Fig. 2 curve Arepresents the input current wave of a particular frequency flowingthrough primary windings 13 and 14: curve B, the voltage variationsproduced in the secondary windings 18 and 19 by the primary current atintensities of primary current in dicated in curve A by broken lines m-mand m'm which are equal to the biasing currents in the primary windings13 and 14; and curve C. the current wave in the output circuit; 27 afterit has passed through a suitable nctwork and having a frequency twicethat of the input circuit. It should be understood that the illustratedrelation between curves B and C is not intended to show the phaserelation between the impulses represented by these curves.

nemesis In Fig. 3 is shown a circuit arrangement wherein a current of aparticular frequency is changed into a current of three times thatfrequency, This arrangement is similar to that shown in Fig. 1 exceptthat an additional high permeability transformer, having no biasingcurrent in its winding, is connected in series with the primary windingsof the other transformers and the secondary wind= ings of the polarizedtransformers are so con nected to each other that the two secondaryvoltage impulses generated in one winding will follow those generated inthe other winding in opposite order as to polarity. .l'n 3 analternating; voltage of a particular frequency is received overconductors l1 and 12 and impressed upon the primary windings 13, 14 and23. Transformers l5 and l6 are oppositely polarized by current from asource 17 as described above for Fig. 1, so that the mutual inductancebetween their primary and secondary windings is maintained at anegligible value except when the alternat ing current in the primarywindings approximately neutralizes the polarizing current in either ofthe windings. The additional high permeability transformer is unbiased.The mutual inductance between its primary winding 23 and secondarywinding 25 therefore rises to a high value for an instant timesdifferent from those of the windings l3 and 14, or every time thealternating current in primary winding 23 passes through amplitudes ofabout zero value. At such times a voltage impulse will be generated inthe secondary winding, in the manner described above. The secondaryWinding 25 is connected in series with the secondary windings 18 and 19in such manner that the induced voltage impulses in winding 25 togetherwith those in windings 18 and 19 will form a uniform series of impulsesof regularly alternating' polarity, The voltage impulses produced in thesecondary windings are short and are separated by somewhat longintervals oi" substantially zero voltages, but by inserting suitablenetwork such as shown in Fig. 3 comprising condensers 20, 21 and 26 andinductance coil 22 in the output circuit 27, the series of shortsecondary voltage impulses may produce a substantially true sinusoidalcurrent wave, and inasmuch as each half cycle of alternating current inthe primary windings 13, 14 and 23 produces three voltage impulses ofalternate polarities, the resultant current in the output circuit 2'?will he of a frequency three times that of the primary current.

Fig. 4 represents graphically the voltages and currents occurring in thecircuit arrangement of Fig". 3. Curve It represents the input currentwave of a certain frequency supplied from a suitable source andimpressed upon the primary windings l3. l and 232 curve B, the shortvoltage impulses produced in secondary windings 25, i8 and ill, theimpulse produced in winding; 25 being inverted with respect to thedirection of variation of the primary current which produces it; andcurve C represents the current produced by the voltage pulses shown bycurve B after it has passed throu h the smoothing networks in the outputcircuit 27, the frequency of this secondary current the primary currentshown in curve A.

In Fig. 5 is shown an arrangement wherein live high permeabilitytransformers are employed for producing an alternating; current oi fivetimes the frequency of the input current. Two of these transformers arepolarized to a certain extent in opposite directions, two others aresimilarly polarized but to a different extent, and the remainingtransformer is unpolarized. In this figure the polarized transformershave been shown with separate windings for effecting the polarization ofeach of the polarized trans formers but it should be understood that thepolarizing current, if desired, may be applied to the primary windingsas shown in Fig. 3. Assuming as hereinbefore that an alternating currentof a certain frequency is received over conductors 11 and 12, thecurrent in this arrangement is passed through the primary windings 13,14, 35, 36 and 23 of transformers ll), 16, 37, 38 and 24; rcspcctivcly.'llransforrners 15, 16, 3'? and 38 are polarized by separate windingsconnected as shown to a common source 17 of direct current, polarizingcurrent for transformers 37 and 38 being made of a lower value than thatfor transformers 15 and 16 by resistance 29 in the polarizing circuit ofthe transformers 37 and 38. The secondary windings l8, 19, 30, 3i and 25of transformers 15, 16, 37, 38 and 24 respectively are connected inseries and form a part of the output circuit 2?. The windings 30 and 31are connected to the other secondary windings 18, 19 and 25 in suchmanner that the induced voltages are inverted. By the insertion orsuitable networks, such as oinprise condensers 20, 21, 32 and 26 andinductance coil 22, the series of voltage impulses induced in thesecondary windings will produce in the output circuit a current or asubstantially pure sinusoidal wave of a frequency five times that oilthe primary current.

ln Fig. 6 curve A represents the input current wave supplied from asuitable means and impressed upon the primary windings 13, 14. 35, 36and 23, shown in Fig. 5, a:m and a2-.v indicating the intensities atwhich the primary current overcomes the polarizing ilux in'translormcrs15 and 16, and 1, 1 and y y indi'ntin the intensities at which theprimary current overcomes the polarizine llun in transformers 37 and 38.Curve B represents the induced voltage impulses in the secondarywindings, the first impulse shown being that produced in winding 25being three times that of All) - when the rising primary current passesthrough its zero value; the second impulse being that produced in andinverted by winding 30 when the primary current reaches amplitude y-y;the third impulse being that produced in winding 18 when the primarycurrent reaches intensity w:r; the fourth impulse is that produced inwinding 19 when the decreasing primary current reaches intensity a: 00after attaining the peak value; the fifth impulse is that produced inand inverted by winding 31 when the primary current passes intensity i gand so on similarly for the impulses produced by the other half cycle ofthe primary current, the impulses forming a uniform series ofalternating potentials. Curve C represents the sinusoidal current waveeffected by the suitable network inserted in the output circuit 27,having a frequency which is a fifth multiple of the frequency of theprimary current.

In Fig. 7 is shown an arrangement wherein the frequency of analternating current is increased ten times by combining the arrangementsof Figs. 1 and 5. The alternating current of a particular frequency isreceived over conductors 11 and 12 and passed through primary windings13 and 14 of transformers 15 and 16 in a wave form such as shown incurve A of Fig. 1. When transformers 15 and 16 are polarized in oppositedirections by passing a direct current from source 17 through windings13 and 14 or through separate windings as shown, the primary currentproduces in the secondary windings 18 and 19 a series of voltageimpulses as shown in curve B of Fig. 2. These impulses after propercorrection by suitable networks produce a sinusoidal current wave of afrequency double that of the input current in conductors 11 and 12.

The sinusoidal wave so produced is passed through primary windings to 44of transformers 46 to respectively. Transformer pairs 46 and 47, and 48and 49 are polarized to a different extent by direct current sources 51and 52 respectively. By arranging the primary windings 40 to 44 and thesecondary windings 53 to 57 in a manner similar to that shown for thewindings in Fig. 5 the voltage impulses induced in the secondarywindings by the current in the primary windings 40 to 44, form a wavehaving five impulses of alternate polarities to each half cycle orimpulse of current in the primary windings 40 to 44. By, means ofsuitable networks a sinusoidal current wave is produced in the outputcircuit of a frequency five times that of the current in primarywindings .40 to 44 and ten times-that of the current in the primarywindings' 13 and 14.

It will be noted in curves A of Figs. 2, 4 and 6 that the input voltageshows a lag in the wave formed at points corresponding to theintensities at which the permeability of the transformer cores reachesits effective values. This is due to the self-induction of the primarywindings which rises to a high value at intervals in which thepermeability is eti'ected and therefore this self-induction momentarilyserves as a high impedance during such intervals. The effects of thisselfinduction is explained in more detail in applicants copendingapplication corresponding to the British Patent 312,338 supra.

Likewise in the same figures of the drawing, the voltage impulses shownin curves B are of the same shape for both polarities, which impulseswhen smoothed out by suitable networks produce a symmetrical wave asshown in curves 0. The fact that the new waves are symmetrical for bothpolarities indicates the absence of the even multiples of the newfrequency.

Various combinations of the arrangements shown may be made in order toincrease the frequency any desired amount, it being understood that incases Where a very high frequency is desired amplifying means such as avacuum tube 60 shown in the output circuit of Fig. 7 may be employed forstrengthening the impulses supplied either to the load or to devices forfurther increases in frequency. In such cases it may also be founddesirable to insert the amplifying means between the secondary windingsand the shaping network.

What is claimed is:

1. In a frequency multiplying device which comprises a winding upon abody of magnetic material, a direct current source connected to causecurrent to flow in at least a part of the winding, an alternatingcurrentsource connected to cause alternating current to flow in at leasta part of the winding, and a load circuit, the method of operation whichcomprises saturating in one direction the body by the direct currentflow in said winding, causing a half cycle of said alternating currentto unsaturate said body and further causin the same half cycle tosaturate said b y in the opposite direction, and causing the same halfcycle to successively unstaturate and saturate said body in the samedirection as in the first operation, whereby a series of impulses equalin number to the number of said unsaturations appear in said outputcircuit.

2. The method of increasing a wave frequency which comprises maintaininga mass of highly permeable material normall magnetically saturated andsuperposing t ereon a periodically reversing magnetizlng force ofcontinuous wave form having higher amplitudes than the force producingthe normally saturated condition to momentarily unsaturate saidmaterial, utilizing successive momentary unsaturated conditions of saidmaterial to form a wave of a higher frequency consisting of electricalimpulses of equal dulll Sill

force, a continuous wave of sed new:

ration and equal maximum amplitudes end of alternately oppositepolarities and 1m pressing said wave of the higher Irequency on a loadcircuit wherein said lose mentioned Wave is smootlned-outv to form,utilizing the whole eneigy produced by the superposed quency whereinonly the odd new frequency are present,

v 3. A method of increasing quency which comprises impre current of apredetermined directions on a plurality of serial coils respectivelymounted on. cthe magnetic circuits in inal-ly maintained in a sotui"superimposing olternetin cuer value end oil defin te steady curient lomolly saturated magnetic ne whereby each-magnetic liei raced in onedirection, is 5333c -i then nesaturated, but i ti-on, to pi oduce duri anegesive svveep o one so rent u plurality of voile vi note opposite polenected coils sespec v imi'ty to the first mentioned mentioned coilslosing connecs cull; in opposite relation vent alternate pairs of adiecenc impressing said impulses on s with successive impulses 0' cos d,A method of inches quency which comprises j y ternating current quencyon serially connected pm ELEM l mgs of a plurality of ti'nnsfo" messcore material of a hi h. pemne -li'ty low magnetizing forces e magneticcircuits of said transformers eing adapted to become saturated atintensities of alternating currentslightly above zero'value,superimposing on the alternatin current in said respective windings steay currents of difiei'ent values to normally maintain said magneticcircuits in saturated condition, the maximum magnetizing force due tothe alternating current minus the magnetizing force due to the directcurrent being suflicient to produce saturation of the cores, whereby 1nresponse to each positive and each negative sweep of sold el-= ternatingcurrent above the values of said steady currents a plurality of short,sharp voltage impulses of equal duration end eoucl maximum amplitudesare produced in serially connected secondary windings e1- ranged on saidtransfiormers, inverting certain of said voltage impulses wherehy theproduced voltage wave is constituted of impulses of alternately oppositepolarities, and impressing said volta e impulses through a smoothing-outnetwori to reduce in a load circuit a uniform sinusoi al curreni; wave &

5., In a frequency changer device, a circuit,-

a plurality of coils connected in series in said circuit and comorisingcores designed to hecome saturate at intensities of current slightlyabove Zeno value, a plurality of other coils connected in series witheach other and connected inductively with first mentioned coils, meansfor transmitting through the first mentioned coils a periodicallyalternating current of a particular (l ency s efiective to produce :1short, sharp ge impulse either of the second inentioned coils every timesaid current thirough intensities near the points of Zion andunsetura'izion of said cores, sai a e impulses being equal dune-biomaximum amplitudes, 2. source normall biasing said first mentioned coilsin o posits (il'lSClllOllS wher by range of amplicudcs v ch the voltageimpulses produced is sted to include any a nsities off alcerneting cur?between :c 1d maximum values, and e circuit racing a smoothing-out neiyvorlz which es the entire energy oi" the impulses produced in saidshifted -mge es continuous poled qual dure'ti and equal oli'tudes.

V H. l l quency changer system, circuit comprising a plui'al ty ofseriall conwhereby each magnetic circuit normally saturated in onedirection is first neutmlized and then saturated in theoppositedirection to produce short, sharp voltage impulses of equalduration end equal maximum amplitudes in either of the second mentionedcoils eveey time said alternating current passes through the intensitiesnear the points of saturation and unsaturation and means for shaping thereproduced Waves to form sinusoidal Wave of increased frequency,

71 in a frequency changer system as set forth in claim 6, other coilsrespectively connected in series with said first and second mentionedcoils, as magnetic circuit for the third mentioned coils arranged to benormally unsaturated, Whereh the periodically elternating current is e'ective to produce a short, shar voltage impulse in the coil connectedto 51s second mentioned coils every ice time the alternating currentpasses through the intensities slightly above or belowzero value tothereby increase the number of impulses produced by each half cycle ofalternating current, and a load circuit including said second mentionedcoils and one of said third mentioned coils wherein certain of saidimpulses are inverted to form in conjunction. with the other of saidimpulses a continuous uniform sine Wave of increased frequency 8. In afrequency changer device, a circuit, a plurality of transformersconnected. in series with said circuit, and comprising cores designed tobecome saturated at an in tensity of current slightly above zero valuemeans for transmitting through the trans former primary windings aperiodically aiternating current of a particular frequency which iseffective produce short, sharpvoltage impulse the transformer seco daryevery time said our cnt passes througl "he intensities near the pointsoi? saturation and nnsatnnation a source 1f current i: biasing the "-r,iiSiOEHlGES in posits (erections wiierebythe range of Eli:- 7 ch onevol impulses are inc. Ede any group of linainniinnv of -mpr ge Wavepolarity I cniced Wave 0 form a sinnso creased ire money,

forth ing its primai y and s contrary Wi SPGCILlVGly connected in seriesW. mary and secondary or sai raliey of trans? iei's, she secondary it@llmOilGii: transform onda: l c

olC BEGUM, n

former arranged to be normally unsaturated whereby the periodicallyalternating current is effective to produce short, sharp voltageimpulses of equal duration and equal maximum amplitudes in the secondarywinding of the last mentioned transformer ever time said alternatingcurrent passes throug 1 intensities slightly above or below zero valueto thereby increase the number of impulses of equal duration and equalmaximum amplitilde produced by each half cycle of alternatcurrent, and.other means for shaping the impulses produced in the secondary Wind oisaid last mentioned transformer to form in conjunction with the voltageimnoises produced in the secondary windings inrality of ransformers acontinua sinusoidal wave of further ining input current, traversed bysaid said coil :1 polariz- 5 said core, the mag- O1 snppiiecl by andsources conneticaliy polarizcaiiy re lllt]

